Sinking Rocks

Trigger warning: trypophobia fuel.

Spotted on the walking path near the Vassar College golf course:

They’re everywhere:

I think the path surface rises as it freezes, then the stones sink into the loosened soil as they warm up. Other parts of the path, generally having more loam / mulch / organic material than mud & pebbles, have an obviously raised / porous / crunchy texture on bitterly cold (by my standards) days.

Surely, someone can pull a PhD thesis from similar observations …